Excavation machinery such as "power shovels", "backhoes" and "ditchdiggers" are well known and widely used. A typical power shovel provides a tractor supporting an articulated arm carrying a "bucket", which typically provides a cutting edge having a plurality of teeth. Such machinery greatly lessens the time required to excavate large quantities of material. However, as will be shown, the structure of the tool supported by the articulated arm may lead an operator to severely damage buried utility lines, often with great resulting injury, damage and expense.
Frequently it is necessary to excavate both above and below a buried utility line, such as a gas or oil pipeline. This work may be required to make repairs in a first utility line, or to install an additional utility line that will cross under existing utility lines. Such excavation is usually quite hazardous, since errors by the machinery operator could result in considerable damage to the pipe being excavated.
Unfortunately, the operator of a typical backhoe or power shovel is frequently unable to see the exact location of the blade portion of the bucket carried by the end of the articulated arm. This is because the backhoe arm typically reaches out over the pipeline, and the open side of the bucket, with its lower edge blade or teeth, is hidden behind the pipeline as the operator removes material from beneath of the pipeline. The "prior art" figure illustrates this typical situation, where the pipeline blocks the operator's view of the bucket. Attempting to use the bucket on the same side of the pipe as the tractor unit of the backhoe would fail, since the open side and the cutting teeth of the bucket face the tractor. If effect, the design of the typical tool attached to the articulated arm of a backhoe is useful only for removing dirt that is between the tractor and the tool attached to the end of the arm. As a result, the operator would be unable to remove material located under the pipe unless the arm reaches over the pipe. Therefore in practice, the operator reaches over the pipe with the articulated arm, and relies on experience and guess-work to tell him where the bucket is in relation to the pipe.
It is therefore the case that there is an urgent need for an attachment tool that is suited for operation with all types of power shovels that allows the operator to clearly see both the attachment tool and the pipeline at the same time. The attachment tool must allow the operator to excavate on the near side of the pipe, i.e. on the same side of the pipe as the tractor unit is on. Such an attachment tool would speed work by allowing the operator to see what he was doing, because the pipe would not be located between the operator and the attachment tool, where the pipe would block the operator's view, as is the case in the prior art. Such an attachment tool would substantially reduce the risk of damage to the pipeline, of explosion, and of injury.